1. Field of the Invention
The present invention relates to a ubiquitous system in which computers are present anywhere, and more particularly to a congestion control access gateway, which interfaces between a Broadband convergence Network (BcN) and a Ubiquitous Sensor Network (USN) including a variety of sensors and terminals and controls a congestion situation in the ubiquitous system, and a congestion control method for the congestion control access gateway.
2. Description of the Related Art
A conventional end-to-end feedback congestion control method can detect and control congestion of terminal nodes only. When congestion occurs, this method cannot immediately deal with the congestion due to a control time required for the transmitter to detect the congestion after the congestion occurs.
A conventional TCP congestion control method requires a longer time to control congestion as the delay time between receiving and transmitting sides increases. In addition, this method may worsen congestion in a high bandwidth network due to packets, which have already been transmitted, until the congestion is detected and a certain process is initiated.
In ubiquitous environments, a variety of sensors may randomly transmit variable-sized data to cause congestion situations. The conventional methods have not taken into consideration these congestion situations and also have not taken into consideration a new environment in which storage features are embedded even in very small sensors along with development of storage technologies.
A congestion control method for a V 5.2 system in an access network was disclosed in Korean Patent Application Publication No. 2001-0056286 (published on Jul. 4, 2001). This method performs congestion control in the following manner. For example, when a congestion situation, in which any more time slots cannot be assigned to a V5.2 link from an access network to a local exchange, has occurred, a threshold congestion level is calculated based on provisioned concentration information, it is detected whether or not the congestion situation has exceeded the threshold congestion level, and a congestion notification signal is transferred to a call sender when the congestion situation has exceeded the threshold congestion level. In this method, if there is no time slot available when attempting call connection using a telephone line, it is determined that a congestion situation has occurred, and a standby request signal is transmitted to the sender, thereby controlling the congestion. However, this congestion control method is not suitable for congestion situations that occur when a variety of wired/wireless sensors randomly transmit variable-sized sensed data.
In a ubiquitous environment in which a very large number of types of sensors are provided, data congestion may occur in abnormal situations such as incidents, accidents, disasters, public performances, and events. For example, if a fire breaks out in a building, not only sensors such as temperature, gas, and wind sensors but also a variety of devices such as mobile phones, cameras, and display devices will transmit data in response to the fire, thereby causing data congestion in a gateway that interfaces between a Broadband convergence Network (BcN) and a Ubiquitous Sensor Network (USN). The conventional congestion control methods have not taken into consideration these congestion situations, which occur when the variety of sensors in the ubiquitous environment randomly transmit variable-sized data, and also have not taken into consideration a new environment in which storage features are embedded even in very small sensors along with development of storage technologies.